Blowing agent composition

ABSTRACT

A blowing agent composition, comprising: (i) azodicarbonamide; (ii) zinc oxide and/or zinc carbonate; and (iii) at least one member selected from the group consisting of zinc salts of C 1  -C 6  organic acids, and C 1  -C 6  organic carboxamides characterized by a high gas evolution rate. The blowing agent composition may be used in effective amounts in formulations containing a foamable polymer to yield an efficiently gas expanded polymeric composition upon exposure to heat. Suitable C 1  -C 6  organic acids for said zinc salts include straight-chain carboxylic acids, and useful organic carboxamides include formamide.

This is a division of application Ser. No. 825,401 filed Mar. 25, 1986now U.S. Pat. No. 4,655,962, Apr. 7, 1987.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved blowing agent composition,comprised of (i) azodicarbonamide: (ii) at least one member selectedfrom the group consisting of zinc oxide and zinc carbonate; and (iii) atleast one member selected from the group consisting of the zinc salts ofC₁ -C₆ organic acids and C₁ -C₆ carboxamides. In other aspects, thisinvention relates to the preparation and use of such blowing agents, aswell as to foamable polymeric compositions comprising foamable polymersand such blowing agent compositions.

2. Description of Related Art

In the manufacture of expanded polymeric materials (such aspolyurethanes, polyolefins and the like) the polymeric material isconventionally mixed with a blowing agent which, upon exposure toelevated temperature conditions, decomposes to form gaseousdecomposition products for expansion of the material.

Amond conventionally employed blowing agents, azodicarbonamide has comeinto widespread usage, largely due to its broad applicability inplastics and elastomers. Moreover, this blowing agent is non-toxic,odorless and non-flammable in character, and its decomposition productspresent no dangerous health hazards. However, azodicarbonamide has thedisadvantage that its decomposition temperature is relatively high, 210°C., rendering it difficult to utilize with many polymericmaterials--particularly those having low softening temperatures or whichare otherwise susceptible to thermal degradation or deterioration.Consequently, when used with polymeric materials having suchdisadvantageous thermal characteristics, it is desirable to add adecomposition accelerator (activator) to lower the decompositiontemperature of the azodicarbonamide blowing agent.

Among the activators useful for reducing the decomposition temperatureof azodicarbonamide are lead, zinc, tin and cadmium oxides, urea andvarious amines. While the use of such activators reduces the otherwiseundesirably high decomposition temperature of azodicarbonamide, suchactivator-containing blowing agent compositions have the disadvantagethat the rate and level of gas evolution at lower temperatures isundesirably low. Specifically, the amounts and rate of gas formed ondecomposition of azodicarbonamide under low temperature activatedconditions are less than those amounts obtained from decomposition ofsuch compound at its normal high decomposition temperature.

As a result of the foregoing disadvantages, azodicarbonamide has beensomewhat limited in the low temperature commercial manufacture of foamed(expanded) products.

It therefore would be highly desirable to provide azodicarbonamide in ablowing agent composition wherein the decomposition temperature for suchcompound is reduced and wherein the adverse impact on the volume of gasand gas evolution rates obtained therefrom is reduced or eliminated.

U.S. Pat. No. 4,312,776 to Puri et al discloses a blowing agentcomposition comprising azodicarbonamide, a chromium sulfate and at leastone zinc compound selected from zinc salts and oxides.

A blowing agent composition comprising (a) azodicarbonamide, (b) zincoxide, zinc carbon or a zinc salt of C₁ -C₄ organic acid, and (c) anaromatic sulfinic acid or a metal salt of an aromatic sulfinic acid isdisclosed in U.S. Pat. No. 4,444,679 to Rowland et al.

Japanese Patent Application No. 53145876-A describes a foamable vinylchloride resin composition utilizing as a foaming assistant at least onezinc salt of C₁ -C₆ organic carboxylic acid and azodicarbonamide.Specific carboxylic acids disclosed in this application include formic,acetic, caproic, tartaric and glycolic acids. The zinc salt is employedat a concentration of 0.5-2 weight percent based on the weight of theresin, which in addition to vinyl chloride polymers may also includeother polymers such as synthetic rubbers.

A process for the production of a cellular polychloroprene vulcanizateusing azodicarbonamide and at least one metal oxide as a blowing agentis disclosed in U.S. Pat. No. 3,846,350.

Japanese Patent Publication No. 133433 discloses a blowing agentcomposition of azodicarbonamide and the reaction product of an aminewith a zinc compound.

Zinc formate compositions are described in British Pat. No. 1,567,417(use of zinc formate in foamable polyester compositions to impartimproved flame retardant properties); U.S. Pat. No. 4,438,223 ( ablowing agent composition comprising zinc formate and certain inorganicand organic alkali metal activators); Dollimore et al, Journal OfInorganic Nuclear Chemistry, 29, 621-627 (1967) (disclosing thedecomposition behavior of zinc and manganous formates); andDjega-Mariabassou et al, Bull. Soc. Chim. France, 9, 3166-3173 (1971),"Study of Decompositions Causing Simultaneous Release of Several Gases,IV--Thermal Decomposition Of Zinc Formate Dihydrate and Morphology ofZinc Oxide Residual" (describing the decomposition behavior of zincformate and the role of zinc oxide formed during its decomposition).German Offenlegungsschrift No. 2,148,099 described the expansion ofthermoplastic polymers using neutral metal salts of formic and/or oxalicacid optionally with a stabilizer such as sodium phosphite.

U.S. Pat. No. 4,554,294 discloses the use of zinc salts of nitro urea inblowing agent compositions.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a chemical blowing agentcomposition comprising (i) azodicarbonamide; (ii) at least one memberselected from the group consisting of zinc carbonate and zinc oxide; and(iii) at least one member selected from the group consisting of zincsalts of a C₁ -C₆ organic acids and C₁ -C₆ carboxamides.

In one preferred aspect, the above-described blowing agent compositioncomprises between about 2 and about 25%, preferably between about 5 andabout 25%, and most preferably between about 10 and about 15% by weightof zinc oxide and/or zinc carbonate and between about 0.5 and about 50%,preferably between about 1 and about 40%, and most preferably betweenabout 1 and about 30% by weight of zinc salt and/or carboxamide, basedon the weight of azodicarbonamide present in the composition.

In another preferred aspect, the blowing agent composition containsamounts of (ii) zinc oxide and/or zinc carbonate and (iii) the zinc saltand/or carboxamide, relative to the amount of (i) azodicarbonamide inthe composition, such that the composition releases at least 150 cm³gas/gram of azodicarbonamide within 15 minutes when heated to 135° C.

In a further aspect, the blowing agent composition contains essentiallyno zinc sulfinate or zinc sulfonate compounds.

Another aspect of the invention relates to a foamable polymericcomposition comprising (a) a foamable polymer, or monomers orco-reactants polymerizable under blowing conditions, and (b) aneffective amount of a blowing agent composition as described above.

Yet another aspect of the present invention relates to a method offorming an expanded polymeric composition comprising blending a foamablepolymer with the blowing agent composition as described above to yield afoamable polymeric composition, and exposing said foamable polymericcomposition to heat to expand the foamable polymer therein and form theexpanded polymeric composition.

A further aspect of the invention relates to a method of making afoamable polymeric composition, comprising blending a foamable polymerwith an effective amount of a blowing agent composition as describedabove.

A still further aspect of the invention relates to a foamed polymericcomposition formed by exposure of a foamable polymeric composition, asas described above, to heat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It has been found that the aforementioned temperature disadvantagesassociated with the use of azodicarbonamide as a blowing agent (viz.,its high decomposition temperature of 210° C.) may be overcome and itsuseful temperature substantially reduced (to low temperatures, e.g., onthe order of about 135° C.) by utilizing azodicarbonamide in combinationwith (a) zinc oxide and/or zinc carbonate and (b) a zinc salt of a C₁-C₆ organic acid and/or a C₁ -C₆ carboxamide. These blowing agentcompositions yield cellular synthetic polymeric materials with highlyuniform cell structure and, further, reduce the tendency of suchpolymeric compositions to blister relative to foams produced with otherknown high gas evolution rate compositions.

The reason for the foregoing improvement in blowing and productcharacteristics is not completely understood, and while we do not wishto be bound by any theory as regards the mechanism of such improvement,it appears that there is a significant synergistic effect associatedwith the intimate contact of the three components (i.e., the (i)azodicarbonamide, (ii) zinc oxide and/or zinc carbonate and (iii) a zincsalt of a C₁ -C₆ organic acid and/or a C₁ -C₆ carboxamide) of theblowing agent composition of the present invention--as will be apparentfrom the data set forth in the Examples hereinafter.

The blowing agent compostion of the present invention thus comprises:(i) azodicarbonamide; (ii) at least one member of the group consistingof zinc carbonate and zinc oxide; and (iii) at least one member selectedfrom the group consisting of zinc salts of C₁ -C₆ organic acids, and C₁-C₆ carboxamides.

Suitable zinc salts useful as component (iii) in the blowing agentcomposition include salts of C₁ -C₆ organic acids such as carboxylicacids. The straight chain carboxylic acids, e.g., formic acid, aceticacid, propionic acid, n-butyric acid, n-valeric acid and n-hexanoicacid, as well as mixtures thereof, are particularly advantageous in thepractice of the present invention.

Among the aforementioned straight-chain carboxylic acids, the preferredC₁ -C₆ organic acid for the zinc salt is formic acid, whereby the zincsalt is zinc formate. Such zinc salt may be provided in the blowingagent composition in the form of anhydrous zinc formate or as zincformate dihydrate, or as mixtures thereof.

Additionally or alternately, component (iii) of the blowing agentcomposition of this invention may comprise a C₁ -C₆ carboxamide. As usedherein, the term "C₁ -C₆ carboxamide" refers to a compound of thestructure R--CON(R₁)₂ wherein each of the R and R₁ substituents may varyindependently of the others and is selected from hydrogen or C₁ -C₆linear or branched alkyl radicals. A particularly advantageouscarboxamide useful in the practice of the present invention isformamide, although other carboxamides such as acetamide, butanamide andN-methylpropanamide and N,N-dimethylbutanamide may also be employed togood effect.

Moreover, mixtures of zinc salts of C₁ -C₆ organic acids and/or of C₁-C₆ carboxamides may be employed as component (iii). In the preferredblowing agent compositions of the present invention, constituent (iii)is either zinc formate or formamide.

With regard to the performance characteristics of respective blowingagent compositions containing these constituents, rapid high volume gasevolution at a temperature of 135° C. (utilized hereinafter as atemperature condition representative of desired commercial processingthermal conditions), is more pronounced in the zinc formate-containingcomposition. Further, the use of zinc formate dihydrate in generalprovides a shorter initiation time for decomposition of azodicarbonamidethan is obtained by the use of anhydrous zinc formate. However, oncedecomposition is achieved, both forms of zinc formate evolve gas atabout equal rates.

As used herein, "zinc formate" is intended to be broadly construed toinclude all forms of zinc formate whether or not combined, complexed orotherwise associated with water, and such term thus includes bothhydrated and anhydrous forms of zinc formate, e.g., anhydrous zincformate as well as zinc formate dihydrate, as well as mixtures of suchforms of the compound, e.g., a mixture of anhydrous zinc formate andzinc formate dihydrate.

The efficacy of the zinc formate-containing blowing agent compositionsof this invention is particularly surprising when one considers thatzinc formate itself if a blowing agent with a decomposition temperatureof about 288° C. It is completely unexpected that one could combine twohigh temperature blowing agents (i.e. azodicarbonamide which decomposesat 210° C. and zinc formate which decomposes at 288° C.) with zinc oxideand/or zinc carbonate and produce a blowing composition with adecomposition temperature of only about 135° C.

Considering further the activating effect of zinc formate onazodicarbonamide, this zinc salt is preferred relative to the zinc saltsof C₂ -C₆ carboxylic acids.

Although the azodicarbonamide constituent of the blowing agentcomposition may be utilized in any form suitable for combination withthe other components of the composition, it is generally preferable toutilize such material in a particulate form. When utilized in such form,the particle size of the azodicarbonamide may be varied according to thegiven end-use application and specific performance and productcharacteristics desired. In general, however, the mean particle diameterof the azodicarbonamide component is typically of the order of betweenabout 0.5 and about 50 microns, and is preferably between about 2 andabout 20 microns. Such azodicarbonamide particle sizes are particularlysuitable in blowing agent compositions utilized to produce cross-linkedexpanded polymers.

The specific concentrations and relative proportions of (i)azodicarbonamide, (ii) zinc oxide and/or zinc carbonate, and (iii) zincsalt of a C₁ -C₆ organic and/or C₁ -C₆ carboxamide in this blowing agentcompositions of the invention may be varied widely, depending upon theparticular response time (i.e., time between exposure to the elevatedtemperature condition utilized, and the initial evolution of gas fromthe composition), gas evolution rate and gas quantity desired. Oneskilled in the art may, however, easily determine by routineexperimentation the preferred proportions for a given expandablematerial and/or end use.

Preferably, for many applications, the blowing agent compositioncomprises sufficient amounts of (ii) zinc oxide and/or zinc carbonateand (iii) zinc salt of C₁ -C₆ organic acid and/or a C₁ -C₆ organiccarboxamide, relative to the amount of (i) azodicarbonamide, such thatthe resulting blowing agent composition evolves at least 150 cm³gas/gram of azodicarbonamide within 15 minutes when heated to 135° C.Such decomposition reaction gas production rate is suitably determinedby the procedure of the following test (hereinafter referred to as the"gas evolution test").

In the gas evolution test, which provides a means of evaluating variousazodicarbonamide activating systems over a range of temperatures or at aset temperature (which, as indicated, is selected as 135° C. herein),the blowing agent composition is first prepared by thoroughly mixing itsconstituents in a Waring blender. To 0.2 gram of the resultingcomposition, 5 milliliters of dioctyl phthalate are added. The mixtureis placed in a gas evolution measuring device, in which thenon-condensable gas released during exposure of the blowing agentcomposition to elevated temperature is collected and measured and themeasured volume corrected to standard temperature and pressureconditions (STP).

In general, the compositions of this invention preferably comprisebetween about 2 and about 25% by weight, more preferably between about 5and about 20% by weight, and most preferably between about 10 and about15% by weight of zinc oxide and/or zinc carbonate, based upon the amountof azodicarbonamide employed. Moreover, such compositions preferablycontain between about 0.5 and about 50% by weight, more preferablybetween about 1 and about 40% by weight of zinc salt and/or carboxamide,based on the weight of azodicarbonamide present in the composition.

The blowing agent composition of this invention may further compriseadditional suitable materials useful for the foaming operation or toachieve performance or structural properties for the product in itsdesired end-use application. Such additional optional components includecatalysts, surfactants, activators (such as urea), extenders,antioxidants, stabilizers, fungicides, bacteriostats, UV absorbers andthe like.

The blowing agent compositions of the present invention may be employedwith any suitable expandable material. Thus, the blowing agentcomposition of the invention may be utilized in an effective amount offoamable polymeric compositions comprising a foamable polymer ormonomer(s) polymerizable under blowing conditions or co-reactantspolymerizable under such conditions. An "effective amount" of theblowing agent composition refers to the amount required to produce thedesired degree of expansion of the expandable material upon exposure toheat.

Expandable materials which may usefully be employed with blowing agentcompositions of this invention include natural and synthetic resins,acrylonitrile-butadiene rubbers and blends of acrylonitrile-butadienerubbers with polyvinylchloride, polyvinylchloride, polyvinylidenechloride, polyvinyl acetate, polyethylvinyl acetate, polyesters,polyolefins (for example, low and high density polyethylene andpolypropylene), modified polyphenylene oxides, polystyrenes,polyacrylates, natural and synthetic rubbers (for example,ethylene-propylene rubber, polyisoprene rubber), copolymers of themonomers amongst themselves or with other monomers (for example,copolymers of ethylvinyl acetate and an olefin such as ethylene orpropylene), and mixtures thereof.

Particularly preferred thermoplastic polymeric materials includepolyolefins (for example, low and high density polyethylene andpolypropylene) and olefin copolymers (for example, copolymers ofethylene and ethylvinylacetate), preferably those which may becross-linked before expansion, for example, by means of chemicalcross-linking agents or by ionizing radiation.

Thermosetting polymer materials which may be used include any type ofsuitable rubber which is curable or vulcanizable to a solid state,exemplified by natural rubber of synthetic rubbery polymers made fromdiolefins such as butadiene and isoprene, or their copolymers withstyrene, acrylonitrile, and the like, as well as butyl rubber,polymerized halo-diolefins, e.g., neoprene, ethylene-propylenecopolymers, ethylene-propylene non-conjugated diene terpolymerelastomers and silicone rubbers.

The blowing agent compositions of the invention find general use infoaming expandable materials, especially those which are capable ofsetting to a normally solid state with sufficient consistency andstrength at the processing temperature (either of themselves or asenabled by any confining device utilized in the blowing operation) toretain the gas evolved from the blowing agent composition and preserve asuitable structure in the expanded product. The processing temperatureutilized in a specific process system will depend upon a number offactors, including the nature of the polymeric material and itsvisco-elastic properties, the forming equipment used, and the nature ofthe end product desired, etc. In general, for most effective results, itis important that that material being expanded has a consistency andtensile strength sufficient to retain, in the case of cellularstructures, the blowing gas in discrete cells, thereby preventingcoalescence of the blowing gas resulting in an undesirable coarse cellstructure. This may generally be obtained in the case of thermosettingresins by adjusting the rate and state of cure to give the compositionthe desired viscosity and strength at the specific gas formingtemperature employed. In the case of thermoplastic resins, the desiredconsistency and strength generally will be achieved by adjusting thetemperature until proper viscosity is obtained. As mentioned, thespecific gas forming temperature utilized in a particular system willvary with the blowing agent composition selected and will be selecteddepending on the polymer or other expandable material involved.

The blowing agent compositions may be mechanically mixed with expandablematerials and, if desired, other customary adjuvants (such as fillers,plasticizers, stabilizers, antioxidants, UV absorbers, and the like)prior to heating the mixture to temperature at which decomposition ofthe blowing agent takes place.

In general, the amount of blowing agent composition used with theexpandable material may vary widely depending on the previouslymentioned factors, as may be determined without undue experimentation byone of ordinary skill in the art. In general, blowing agent compositionconcentrations of between about 0.05 and about 20% by weight, with mostpreferred concentrations typically being between about 1 and about 10%by weight, based on the total weight of the foamable polymer, areemployed.

Thus, a foamable polymeric composition may be formed by blending afoamable polymer with an effective amount of a blowing agent compositionaccording to the invention. Upon blending the foamable polymer with suchblowing agent composition, the resulting foamable polymeric compositionmay be exposed to heat to expand the foamable polymer and form anexpanded polymeric composition. Depending on the blowing conditions andspecific composition of the blowing agent formulation, expandedmaterials having specific density and other physical and performancecharacteristics of widely varying character, as necessary and/or desiredin a given end-use application, may be produced.

The features and advantages of the present invention are furtherillustrated with respect to the following non-limiting Examples, whereinall parts and percentages are by weight, unless otherwise expresslystated.

EXAMPLE 1-3 AND COMPARATIVE EXPERIMENTS A-E

Cumulative gas evolution was measured at various times for severalblowing agent compositions each comprising azodicarbonamide (ADC) andzinc formate dihydrate and/or zinc oxide in the amounts indicated inTable I below. The results of such testing are also summarized in TableI.

                                      TABLE I                                     __________________________________________________________________________                Example or Comparative Experiment                                             A  B  C  D   E   1  2  3                                          __________________________________________________________________________    ADC, parts  100                                                                              100                                                                              100                                                                              100 100 100                                                                              100                                                                              100                                        Zinc formate dihydrate,                                                                    1 11 18 --  --   1  6  13                                        parts                                                                         Zinc Oxide, parts                                                                         -- -- -- 11  18  11  12                                                                               13                                        Total Gas Evolved at                                                          135° C., cm.sup.3 /g of                                                composition Minutes                                                           3           --  4 -- --  --   2  4  7                                         6            6 19 15 --  --  13  18                                                                               72                                        9            9 36 39 1   1   33 125                                                                              175                                        12          12 54 58 1   2   61 170                                                                              180                                        15          14 70 75 1   2   116                                                                              172                                                                              181                                        Total Gas Evolved                                                                         14 78 89 1   2   130                                                                              203                                                                              228                                        After 15 Minutes at                                                           135° C., cm.sup.3 /g of ADC                                            __________________________________________________________________________

The above data show that the three component blowing agent compositionsof this invention produces greater quantities of gas more quickly thando compositions comprising only ADC and zinc formate or zinc oxide.

EXAMPLES 4-7 AND COMPARATIVE EXPERIMENTS F-I

Using the gas evolution test, total gas evolution at 135° C. wasdetermined for blowing agent compositions comprising variousconcentrations of azodicarbonamide zinc formate dihydrate and/oranhydrous zinc formate and/or zinc oxide. The results are indicated inTable II below.

                                      TABLE II                                    __________________________________________________________________________                Example or Comparative Experiment                                             F  G  H  I   4   5  6  7                                          __________________________________________________________________________    ADC, parts  100                                                                              100                                                                              100                                                                              100 100 100                                                                              100                                                                              100                                        Zinc formate dihydrate,                                                                   11 --  25                                                                              --   6  --  13                                                                              --                                         parts                                                                         Anydrous Zinc formate,                                                                    -- 11 -- 25  --   6 --  13                                        parts                                                                         Zinc Oxide, parts                                                                         -- -- -- --   12  12                                                                               13                                                                               13                                        Total Gas Evolved at                                                          135° C., cm.sup.3 /g of                                                composition Minutes                                                           3            4 11  7  2   4   2  7 --                                         6           19 16  25                                                                              15   18  23                                                                               72                                                                               19                                        9           36 34  56                                                                              38  125 111                                                                              175                                                                              168                                        12          54 56  91                                                                              71  170 215                                                                              180                                                                              179                                        15          70 79 121                                                                              102 172 217                                                                              181                                                                              182                                        Total Gas Evolved                                                                         78 88 151                                                                              128 203 256                                                                              228                                                                              229                                        After 15 Minutes at                                                           135° C., cm.sup.3 /g of ADC                                            __________________________________________________________________________

The above data indicate that three component blowing compositions whichcomprise zinc oxide in addition to azodicarbonamide and either zincformate dihydrate or anhydrous zinc formate are superior to twocomponent blowing compositions not containing zinc oxide.

EXAMPLES 8-11 AND COMPARATIVE EXPERIMENT J-P

Additional blowing agent compositions were prepared containing variousconcentrations of formamide, as shown in Table III, and the total gasevolution at 135° C. was determined for each of such samples.

                                      TABLE III                                   __________________________________________________________________________                Example or Comparative Experiment                                             J   K   L   M   N   P   8  9  10 11                               __________________________________________________________________________    ADC, parts  100 100 100 100 100 100 100                                                                              100                                                                              100                                                                              100                              Zinc Oxide, parts                                                                         --  --  --  11  18  43   6 13 19 12                               Formamide, parts                                                                          5   18  43  --  --  --  19 13  6  6                               Total Gas Evolved at                                                          135° C., cm.sup.3 /g of                                                composition Minutes                                                           3           --  --  1   --  --  --  -- -- --  3                               6           --  1   2   --  --  2   20 16 11 13                               9           --  2   3   1   1   2   42 45 27 25                               12          --  2   5   1   2   2   68 96 56 50                               15          --  2   6   1   2   2   89 150                                                                              112                                                                              95                               Total Gas Evolved                                                                         0   2   9   1   2   3   111                                                                              189                                                                              140                                                                              112                              After 15 Minutes at                                                           135°  C., cm.sup.3 /g of ADC                                           __________________________________________________________________________

The above data once again demonstrate the synergystic effect at lowertemperatures of about 135° C. of the three component blowing agent ofthis invention.

In the following Examples, the ingredients utilized in variouscompositions are identified with reference to the designations shown inTable IV below.

                  TABLE IV                                                        ______________________________________                                        Ingredients                                                                   ______________________________________                                        SBR-1    Styrene-Butadiene (24.5% bound styrene)                                       Synpol 1502, Synpol, Inc.                                            SBR-2    Styrene-Butadiene (58.0% bound styrene)                                       Polysar SS255, Polysar Limited.                                      NBR      Acrylonitrile-Butadiene (32.5% ACN) Paracril                                  BJLT, Uniroyal, Inc.                                                 PVC      Polyvinyl Chloride (Tenneco 175) Tenneco                                      Chemical Co.                                                         Extender Oil                                                                           Naphthenic Oil, ASTM D2226, Type                                              103 (Circosol [TM] 4240).                                            Plasticizer-1                                                                          (Santicizer 154) Monsanto Co.                                        Plasticizer-2                                                                          Dioctylphthalate.                                                    Carbowax Polyethylene glycols (Carbowax 4000) Union                                    Carbide Corp.                                                        Plasticizer-3                                                                          Chlorinated paraffins, 70% chlorine by wt.                                    (Chlorowax 70) Diamond Alkali Co.                                    Stabilizer-1                                                                           Soybean oil epoxide (Paraplex G-62, sp. gr.                                   0.993 at 15° C.) Rohm & Haas Co.                              Stabilizer-2                                                                           Chemical heat stabilizer (Mark 189A) Argus                                    Chemical Corp.                                                       Resin    Aromatic resin (Picco 100) Hercules, Inc.                            Antioxidant-1                                                                          Octylated diphenylamine (Octamine [TM])                                       Uniroyal, Inc.                                                       Antioxidant-2                                                                          Tri(mixed mono-dinonyl)phenyl phosphite                                       (Polygard [TM]) Uniroyal, Inc.                                       Accelerator-1                                                                          N--cyclohexyl-2-benzothiazole sulfenamide                                     (Delac-S [TM]) Uniroyal, Inc.                                        Accelerator-2                                                                          Zinc salt of 2-mercaptobenzothiazole                                          (OXAF [TM]) Uniroyal, Inc.                                           Accelerator-3                                                                          Zinc dimethyldithiocarbamate (Methazate [TM])                                 Uniroyal, Inc.                                                       Accelerator-4                                                                          Dipentamethylene thiuram tetrasulfide                                         (Sulfads [TM]) R. T. Vanderbilt Co., Inc.                            Filler-1 Hydrated Silica (Hi-Sil 233) PPG Industries,                                  Inc.                                                                 Filler-2 Clay, sp. gr. 2.6; particle size: ca. 95%                                     less than 2 micron (Suprex Clay [TM] J. M.                                    Huber Corp.                                                          Filler-3 Hydrated alumina pigment (Hydral 710)                                         Aluminum Company of America.                                         Filler-4 Ultra-fine magnesium Silicate (Mistron Vapor                                  [TM] Sierra Talc Co.                                                 Carbon Black                                                                           N550 FEF black                                                       ADC      Azodicarbonamide; av. particle size: 3                                        micron (Celogen [TM] AZ130) Uniroyal, Inc.                           DNPT     Dinitrosopentamethylene tetramine Opex 93,                                    Olin                                                                 Urea MB (.75)                                                                          Urea masterbatch 75% active BIK-OT [TM]                                       R-464, Ware Chemical Corp.                                           ZPTS     Zinc p-toluene sulfinate                                             ZFDH     Zinc formate dihydrate                                               AZF      Anhydrous zinc formate                                               FA       Formamide                                                            DPG MB-352                                                                             Diphenylguanadine MB-65% T(DPG) D65,                                 (.65)    Wyrough and Loser, Inc.                                              ______________________________________                                    

EXAMPLES 12-14 AND COMPARATIVE EXPERIMENT Q

Two rubber masterbatches were prepared using the following recipes:

    ______________________________________                                                     Parts by Weight                                                  ______________________________________                                        Masterbatch-1                                                                 SBR-1          70                                                             SBR-2          60                                                             Filler-1       30                                                             Filler-2       100                                                            Resin          10                                                             Antioxidant-1  2                                                              Stearic Acid   1                                                              Zinc Oxide     5                                                              Extender Oil   10                                                             Total parts    288                                                            Masterbatch-2                                                                 NBR            50.0                                                           PVC            50.0                                                           Stabilizer-1   3.0                                                            Stabilizer-2   2.0                                                            Antimony Oxide 5.0                                                            Filler-3       60.0                                                           Antioxidant-2  1.0                                                            Plasticizer-1  15.0                                                           Filler-1       25.0                                                           Filler-4       24.0                                                           Carbon Black   10.0                                                           Zinc Oxide     8.0                                                            Antioxidant-1  1.0                                                            Plasticizer-2  15.0                                                           Plasticizer-3  15.0                                                           Total parts    284.0                                                          ______________________________________                                    

Blowing agent compositions of the invention (Examples 12-14) wereevaluated for the expansion of press molded cellular shoe soling whilesimultaneously curing the polymeric material, versus a compositioncomprising a conventional blowing agent, dinitrosopentamethylenetetramine. The compositions and results for these Samples are set forthin Table V below.

                  TABLE V                                                         ______________________________________                                        Example or Compara-                                                           tive Experiment                                                                            Q        12       13     14                                      ______________________________________                                        Masterbatch-1                                                                              288.00   288.00   288.00 288.00                                  Delac-S      0.80     0.80     0.80   0.80                                    DPG MB-352 (.65)                                                                           0.45     0.45     0.45   0.45                                    Sulfur       2.50     2.50     2.50   2.50                                    BIK-OT MB-464 (.75)                                                                        3.20     1.33     1.33   1.33                                    Carbowax     1.00     1.00     1.00   1.00                                    Blowing Agent*                                                                             4.00     5.00     5.00   5.00                                    Total        299.95   299.08   299.08 299.08                                  Precure 11 min.                                                               163° C.                                                                Density, g/cm.sup.3                                                                        0.47     0.44     0.45   0.49                                    Compression Set,                                                                           12       13       14     17                                      50% RT 22 HOurs, %                                                            Shrinkage 6 hrs.                                                                           2.7-1.0  1.0-1.25 1.25-0.5                                                                             0.75-1.0                                100° C. L & W %                                                        Average      1.85     1.12     0.88   0.88                                    ______________________________________                                         *In Comparative Experiment Q, the blowing agent was DNPT. In Examples         12-14, the blowing agent comprised 4.25 parts ADC, 0.50 part zinc oxide       and 0.25 part of either ZFDH (in Example 12), AZF (in Example 13) or FA       (in Example 14).                                                         

The above data show that decreased shrinkage is encountered in blowncompositions produced employing the blowing agent of this inventionrelative to a commercially employed blowing agent, DNPT.

EXAMPLE 15

The usefulness of blowing agent compositions of the invention (Example15) was further evaluated in insulation tubing using the followingrecipe, all in parts by weight, with the results shown in Table VIbelow.

                  TABLE VI                                                        ______________________________________                                        Masterbatch-2     284.0                                                       Sulfur            2.3                                                         Accelerator-4     1.7                                                         Accelerator-3     1.5                                                         Accelerator-2     0.6                                                         Blowing Agent*    31.0                                                        Total parts       321.1                                                       Density, g/cm.sup.3                                                           Precure 4 in/127° C.                                                                     0.082                                                       plus 8 min/149° C.                                                     10 min/149° C.                                                                           0.070                                                       6 min/127° C.                                                                            0.082                                                       plus 8 min/149° C.                                                     ______________________________________                                         *The blowing agent comprised 26.4 parts ADC, 3.1 parts zinc oxide and 1.5     parts ZFDH.                                                              

This data shows that insulation having desirable properties may beproduced employing the blowing agents of this invention.

What is claimed is:
 1. A foamable polymeric composition, comprising (a)at least one member selected from the group consisting of foamablepolymers and monomers or coreactants polymerizable under blowingconditions, and (b) an effective amount of a blowing agent composition(i) azodicarbonamide; (ii) at least one member selected from the groupconsisting of zinc oxide and zinc carbonate; and (iii) at least onemember selected from the group consisting of zinc salts of C₁ -C₆organic acids, and C₁ -C₆ carboxamides.
 2. The foamable polymericcomposition according to claim 1, wherein said foamable polymer ispolyurethane.
 3. The foamable polymeric composition according to claim1, wherein said foamable polymer is a polyolefin.
 4. The foamablepolymeric composition according to claim 1, wherein said foamablepolymer is a cross-linked expandable polyolefin.
 5. The foamablepolymeric composition according to claim 1, wherein said foamablepolymer is a natural or synthetic rubber.
 6. The foamable polymericcomposition according to claim 1, wherein said foamable polymer isselected from polyvinylchloride; acrylonitrile-butadiene rubbers; blendsof acrylonitrile-butadiene rubbers with polyvinylchloride;polyvinylidene chloride; polyvinylacetate; polyethylvinyl acetate;polyesters, polyolefins; polyphenylene oxides; polystyrenes;ethylene-propylene rubber; polyisoprene rubber; polymers ofhalo-diolefins; polyamides; polyacrylates; copolymers of monomers of theforegoing polymers; and mixtures of the foregoing.
 7. The foamablepolymeric composition according to claim 1, wherein said foamablepolymer is elastomeric or thermoplastic.
 8. The foamable polymericcomposition according to claim 1, wherein the concentration of saidblowing agent is from about 0.05 to about 20% by weight, based on theweight of said foamable polymer.
 9. The foamable polymeric compositionaccording to claim 8, wherein the concentration of said blowing agent isfrom about 0.1 to about 15% by weight, based on the weight of saidfoamable polymer.
 10. The foamable polymeric composition according toclaim 9, wherein the concentration of said blowing agent is from about 1to about 10% by weight, based on the weight of said foamable polymer.